The present invention relates to a reagent for measuring immune complexes fixed with an anti-C3 antibody-Facb fragment, useful for the quantitative measurement of immune complexes (antigen antibody complexes) which exist in the blood, blood plasma, or other body fluids of a patient suffering from an immune complex disease, and also to a method of immunologically measuring immune complexes by use of the reagent.
Immune complex diseases can be classified into two categories of diseases: one resulting from such an endogenous autoantigenic causation as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), chronic glomerulonephritis, and tumor, and the other resulting from such an exogenous antigenic causation as acute glomerulonephritis and leukemia. The formation of an immune complex is one of the defense reactions which take place in living body and the immune complex is taken in the reticuloendothelial cells or other phagocytes to be quickly disposed of after its formation in a healthy body. But once the antigenic stimulation continues so long as to cause the mass formation of immune complexes or to allow the formed immune complexes to behave beyond control of the reticuls-endothelial system, etc., they start settling themselves in the blood, blood serum, or body fluid, and finally deposit on the tissue, thus leading it to histological destruction. Therefore, the quantitative measurement of immune complexes existing in the blood, blood serum, or body fluid provides important and useful information in making a diagnosis and setting up a proper method of medical treatment.
Various methods are presently known for quantitatively measuring immune complexes existing in the blood and body fluid and they may fall into two groups, i.e., methods which are conducted physiochemically and those which are based on biologically characteristic factors as shown below.